Induction sealing plastic parts together by heating metal embedded in one of the plastic parts, or by heating metal components clamping the parts together, is old in the art. Heat is developed by generating a high frequency oscillating magnetic field in the presence of the metal. Depending on the metal, either eddy current losses or magnetic hysteresis losses are believed responsible for heating the metal. Heat from the metal is then conducted through the plastic parts to their sealable interface. Plastics may melt or become tacky due to the conducted heat. If the plastic materials are compatible and sufficient pressure is applied, the plastic parts can be bonded together. Once the magnetic induction field is removed, the heat may be dissipated from the sealable interface through the plastic parts. Cooling the sealable interface under pressure is generally required to produce a strong seal. The great benefit of the induction heating process is that heat can be quickly generated so that high production rates can be achieved.
Processes for sealing webs together using induction sealing are also old in the art. For example, U.S. Pat. No. 3,461,014 to James discloses a process in which ferrous oxide particles small enough to be mixed with conventional printing ink are printed onto a substrate. The substrate and web are combined and passed through a magnetic induction field to heat the ferrous oxide particles between the substrate and web. Then the web and substrate are passed through a pair of "squeeze rollers" to generate sufficient pressure to seal the webs together.
In the present invention metal particles are preferably added to a heat-activated adhesive, such that when the adhesive is placed between two plastic parts, the adhesive is induction heat-activated to bond the two plastic parts together.
Squeezebottle dispensers having fluid-containing, flexible inner bags within them are common in the art. When a squeezebottle dispenser is squeezed, fluid is forced from the flexible inner bag through a discharge opening at the top of the dispenser. Valving in the dispenser enables air to be compressed within the squeezebottle during squeezing, but valving then allows air to vent into the bottle to replace the dispensed fluid after the squeezebottle is released. Repeated squeezing cycles cause the flexible inner bag to collapse around the fluid within the squeezebottle as the flexible inner bag empties.
A problem with such dispensers is that a flexible inner bag tends to collapse most quickly near its discharge opening. This is believed to be due to higher velocity fluid flow near the discharge opening causing lower static pressure there. Fluid flow may be choked off From the rest of the flexible inner bag if the flexible inner bag collapses prematurely near the discharge opening. To correct this problem, the manner in which the flexible inner bag can collapse is generally controlled. For example, a flexible inner bag may be designed to collapse radially about a perforated diptube connected to the discharge opening of the squeezebottle. In some circumstances, for example, when the fluid is highly viscous like toothpaste, diptubes generally provide too much resistance to fluid flow through them. For such fluids, which have viscosities great enough that they cannot flow under gravity, another collapse control approach is often used. That is, a flexible inner bag is affixed to the upper half of the inside of a squeezebottle so that the flexible inner bag can collapse by inverting axially toward the discharge opening. Flexible inner bag inversion offers minimum flow resistance.
For squeezebottle dispensers having flexible inner bags which invert toward the discharge opening, there is often a construction problem involved with inserting and affixing the flexible inner bag inside the squeezebottle. Affixing the bag typically involves heat sealing. The finish of the squeezebottle usually has a discharge opening smaller in circumference than the body of the squeezebottle so that the bottle finish may later be capped with a reasonably sized closure. If the flexible inner bag is inserted into the squeezebottle From a small diameter discharge opening, it may be difficult to insert a heat sealing tool into the flexible inner bag to seal the flexible inner bag to the upper half of the squeezebottle. A sealing tool would be expected to expand to press the flexible inner bag against the inner side wall of the squeezebottle. A reliable, high speed method for affixing a flexible inner bag to the inside of a squeezebottle, using an expanding tool, has been unavailable in many cases.
Alternatively, if the bag is inserted from the opposite end of the squeezebottle, which is usually the bottom of the squeezebottle, the bag must later be filled and sealed closed from the bottom end, and a bottom piece must be added to close the open bottom of the squeezebottle. For example, twisting the open end of the bag after filling and then heat sealing the twisted portion is one approach to closing a filled bag. Closing the bag after filling may also be a slow and difficult process.
One solution to the bag filling and closing problem is a construction that seals a half bag to the midline circumference of a squeezebottle. A half bag may be inserted from the open bottom of the squeezebottle with its closed end at the discharge opening of the squeezebottle. After sealing the open end of the half bag to the midline circumference of the squeezebottle, the half bag may then be inverted so that its closed end is positioned at the bottom of the squeezebottle. Filling may then be accomplished from the discharge opening of the dispenser. Such a construction requires a complete seal around the midline circumference of the squeezebottle.
The half bag approach enables conventional high speed filling without subsequent bag closing and sealing. However, the half bag approach also requires the formation and handling of a half bag and the inversion of the half bag after sealing it to the squeezebottle. Bag forming and internal sealing operations may be complex and difficult even when performed manually.